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首页> 外文期刊>Acta crystallographica. Section D, Biological crystallography. >A novel member of glycoside hydrolase family 30 subfamily 8 with altered substrate specificity
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A novel member of glycoside hydrolase family 30 subfamily 8 with altered substrate specificity

机译：一种新型糖苷水解酶家族的成员30亚科8与底物特异性改变

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摘要

Endoxylanases classified into glycoside hydrolase family 30 subfamily 8 (GH30-8) are known to hydrolyze the hemicellulosic polysaccharide glucuronoxylan (GX) but not arabinoxylan or neutral xylooligosaccharides. This is owing to the specificity of these enzymes for the alpha-1,2-linked glucuronate (GA) appendage of GX. Limit hydrolysis of this substrate produces a series of aldouronates each containing a single GA substituted on the xylose penultimate to the reducing terminus. In this work, the structural and biochemical characterization of xylanase 30A from Clostridium papyrosolvens (CpXyn30A) is presented. This xylanase possesses a high degree of amino-acid identity to the canonical GH30-8 enzymes, but lacks the hallmark beta 8-alpha 8 loop region which in part defines the function of this GH30 subfamily and its role in GA recognition. CpXyn30A is shown to have a similarly low activity on all xylan substrates, while hydrolysis of xylohexaose revealed a competing transglycosylation reaction. These findings are directly compared with the model GH30-8 enzyme from Bacillus subtilis, XynC. Despite its high sequence identity to the GH30-8 enzymes, CpXyn30A does not have any apparent specificity for the GA appendage. These findings confirm that the typically conserved beta 8-alpha 8 loop region of these enzymes influences xylan substrate specificity but not necessarily alpha-1,4-xylanase function.
机译：Endoxylanases分为糖苷水解酶家庭30亚科8 (GH30-8)是已知的水解的hemicellulosic多糖glucuronoxylan (GX)但不是阿糖基木聚糖或中性xylooligosaccharides。这些酶的特异性alpha -, 2-linked葡萄糖醛酸酯(GA)附件GX。一系列aldouronates每个包含一个遗传算法代替木糖的倒数第二减少终点站。30和木聚糖酶的生化特性从papyrosolvens梭状芽胞杆菌(CpXyn30A)提出了。规范GH30-8氨基酸的身份酶,但缺乏标志β8-alpha 8循环地区部分定义的功能这GH30亚科在GA及其作用识别。在所有木聚糖基质同样低的活动,而水解xylohexaose显示竞争转糖基作用的反应。结果与模型直接比较XynC GH30-8酶从枯草芽孢杆菌。尽管其高序列GH30-8身份酶,CpXyn30A没有任何明显GA附体的特异性。确认通常守恒的β8-alpha8圈地区的木聚糖酶的影响底物特异性,但不一定alpha -, 4-xylanase函数。

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